Shear stable barium 12-hydroxy stearate grease containing a boron ester compound



United States Patent O SHEAR STABLE BARIUM 12-HYDROXY STEARATE gllggSE CONTAINING A BORON ESTER COM- Harry J. Worth, Fullerton, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Filed Mar. 21, 1958, Ser. No. 722,834

11 Claims. (Cl. 252-40.7)

This invention relates to lubricating grease compositions and particularly lubricating greases containing barium soaps. More particularly it relates to barium l2- hydroxy stearate greases having incorporated herein additive materials which improve mechanical stability, increase melting point and shear stability and impart reversibility characteristics to the grease.

Simple barium soap greases consisting of mineral lubricating oil containing simple barium soap have not been found satisfactory as lubricants primarily in that they do not have good mechanical stability and they are not reversible.

Attempts to produce simple barium soap greases have included the use of the barium soap l2-hydroxystearic acid. Although products having good grease consistencies at ordinary temperatures are produced with barium l2-hydroxy stearate, these greases are not reversible, they have relatively low dropping points and they require large proportions of soap in order to obtain reasonable penetration values.

An object of this invention is to produce a barium soap grease which has a high melting point, a low soap content for a given penetration, good reversibility and good shear stability.

Another object of this invention is to produce a barium soap grease having the mentioned characteristics using barium 12-hydroxy stearate as the thickening agent.

A further object of this invention is to provide a method of producing a barium 12-hydroxy stearate grease having the above described characteristics.

Other objects, features and advantages of this invention will be apparent from the description which follows:

It has been found that a grease having all of the above characteristics is obtained by adding to barium 12-hydroxy stearate grease, or including as part of the composition of such a grease, a small amount of a boron compound prepared by reacting orthoboric acid with an ester of the class consisting of glycol and polyglycol, mono and di-esters of hydroxy fatty acids and glycerol, mono, di and tri-esters of hydroxy fatty acids. This reaction is effected at somewhat elevated temperatures as will be discussed later. It will be noted that the term boric acid when used herein is used in its ordinary sense and it means orthoboric acid, H BO The structure of the boron compound is not known but the product is believed to be an ester of boric acid in which two of the acid groups of the boric acid are esterified with the hydroxyl groups present in the above mentioned esters of glycol, polyglycol and glycerol with hydroxy fatty acids.

Compounds useful in preparing the boron compounds or boron esters, that is, which may be reacted with orthoboric acid to produce the desired compounds include ethylene glycol mono-l2-hydroxystearate, ethylene glycol monoricinoleate, ethylene glycol di-lZ-hydroxy stearate, ethylene glycol di-9,IO-dihydroxystearate, propylene glycol mono-12-hydroxystearate, propylene glycol di-9,10-dihydroxystearate, propylene glycol diricinoleate,

propylene glycol di-12-hydroxystearate, diethylene glycol mono-12-hydroxystearate, dipropylene glycol di-12-hydroxystearate, dibutylene glycol mono-9,10-dihydroxystearate, triethylene glycol mono-9,IO-dihydroxystearate, glycerol mono-12hydroxystearate, glycerol di-l2-hydroxystearate, glycerol tri-12-hydroxystearate, glycerol mono- 9,10 dihydroxy stearate, glycerol di 9,10 dihydroxystearate, glycerol tri-9,IO-dihydroxystearate and glycerol triricinoleate. Other compounds include the glycol, polyglycol and glycerol esters of mixed hydroxy fatty acids having between about 8 and about 50 carbon atoms per molecule such as those obtained by oxidizing refined paraflin wax in the liquid phase with air at temperatures between about C. and about C. at 100 pounds pressure until the acid number of the product is between 240 and 300 mg. KOH/g., and separating a naphtha-insoluble, water-insoluble fraction. Such acids and their method of preparation are described in United States Patent No. 2,606,890. This patent shows also methods of preparing glycol and glycerol esters of these acids. Thus, hydroxy fatty acids having from about 8 to about 50 or more carbon atoms per molecule, may be employed in forming the glycol, polyglycol or glycerol esters or partial esters. Any of these esters may then be reacted with orthoboric acid to produce the boron ester compounds suitable for addition to greases thickened with barium 12-hydroxystearate to improve the characteristics described herein.

In preparing the boron esters of the above compounds, the hydroxy fatty acid esters are reacted with orthoboric acids at temperatures between about 215 F. and about 425 F. and preferably between about 250 F. and about 400 F. for a period of about 0.25 hour to about 2 hours. The heating is now carried out in an open vessel which is preferably equipped with means for stirring or I agitating or mixing the reactants and also with means for heating. A steam jacket or an electrically heated kettle, such as the one used for grease making, is very satisfactory. When the heating is finished and the reaction completed, the product is clear and entirely free from unreacted solid boric acid. When cooled to room temperature, the product is liquid to solid depending on the hydroxy fatty acid ester employed.

The boron compounds or esters produced in this manner are generally soluble in mineral lubricating oil, and it is, therefore, possible to prepare oil concentrates of these compounds which are somewhat more readily handled and thus more readily incorporated in grease compositions than are the compounds themselves. As a modification of the above method of preparing the cornpounds following the heat treatment, mineral lubricating oil such as one to be used in preparing grease is added to the boric acid-hydroxy fatty acid ester product while it is still warm and mixing continued until the boron compound is dispersed and/or dissolved in the oil. Concentrates containing between about 10% and about 50% or more by weight of the boron ester compound in lubricating oil can thus be prepared. On cooling a liquid or semisolid, concentrate is thus obtained.

The reaction ratio of hydroxy fatty acid ester to orthoboric acid is one chemical equivalent of the ester based on hydroxyl groups present in the fatty acid residues as well as in the glycol, polyglycol or glycerol residue of the esters to 1.5 equivalents of the orthoboric acid. Thus in reacting glycerol tri-12-hydroxystearate with orthoboric acid, 1 mole of the ester will be reacted with 1.5 moles of the acid. Increasingly, 1 mole of the ethylene glycol mono-12-hydroxystearate will be reacted with 1 mole of orthoboric acid. While the indicated reacting ratio is the most desirable, this one can be varied somewhat and a satisfactory product will be obtained. Thus for each equivalent, or stated another way, for each bydroxyl group of the hydroxy fatty acid ester between about 1.4 and 1.7 equivalents of the boric acid should be employed.

In pre aring the finished grease of this invention a grease kettle is charged with l2-hydroxystearic acid and preferably between about 20% and about 40% by weight of the total lubricating oil which is to be used in preparing the grease batch and this mixture is heated to a temperature of about 150 F. to about 205 F. To this heated mixture is added an amount of a basic barium compound such as the oxide or hydroxide, preferably a hydrated oxide or hydroxide such as barium hydroxide pentahydrate, sufficient to completely neutralize the acid. A small amount of water is generally added along with the barium hydroxide although this is not essential when a hydrate form of base is used. Heating and agitating is continued during the neutralization reaction which occurs rapidly. The mixture is then heated to a maximum temperature of about 360 F. while adding the remaining lubricating oil necessary to complete the grease formulation.

The boron ester compound, as such or in the form of an oil concentrate, can be added at substantially any time during the grease preparation following neutralization of 12-hydroxystearic acid. Preferably it is added at some time during the heating following soap formation and before the maximum temperature has been reached.

The amount of boron compound to be added will be between about 0.05% and about 5.0% by weight of the total composition, preferably between about 0.1% and 2.0% by weight of the boron compound will be employed based on the weight of the grease.

Although barium l2-hydroxy stearate greases to which one of the boron ester compounds described herein has been added is a highly mechanically stable grease and has the desirable characteristics described, it is found that improvement in these characteristics can be attained by including in the grease composition a small amount, e.g. 0.01% to 0.5% by weight, based on the grease, of triethanolamine. This compound may be added to the grease composition at any time following completion of the soap forming reaction such as during the heating and reduction of the grease.

Substantially any grade or type of mineral lubricating oil may be employed, thus oils as light as transformer oils and oils as heavy as bright stock produce greases having the desired characteristics. Generally an oil of S.A.E. grade 1040 or 50 will be used, and these oils will preferably be refined products such as solvent extracted oils having a viscosity index (V.I.) greater than about 10. A solvent treated western naphthenic mineral lubricating oil of S.A.E. 20 or 30 grade having a viscosity index of about 25 is a particularly satisfactory oil. Other oils which are entirely satisfactory are solvent treated and dewaxed western parafiinic mineral lubricating oils having a viscosity index of 80 to 90.

The percentage of soap in the finished grease will generally be between about 3% and about 25-30% by weight. Usually between about 5% and about 20% of soap will give the amount of thickening desired in a grease for most purposes.

As is well understood in the art, small amounts of oxidation inhibitors may he added to the grease. Generally between about 0.2% and about 1% by weight of a conventional oxidation inhibitor such as hydrocarbon substituted diphenyl amine will be used. A particularly satisfactory commercial inhibitor consisting of octylated diphenyl amines is obtainable from R. T. Vanderbilt Inc., under the name of Agerite Stalite." Phenyl alphanaphthylamine is also a very satisfactory inhibitor. Other well known commercial inhibitors may be used with satisfaction.

Penetration values described herein are determined by means of the Shell micro penetrometer. This apparatus and its method of use are described in The Institute Spokesman for March 1943, volume VI, No. 12, pages 1, 4 and 5.

Shear stability of the greases described in the examples herein is determined by means of the Shell roll test. The required apparatus and the method of carrying out this test are described in the Institute Spokesman reference cited in the preceding paragraph. In this test, which measures the tendency of a grease to soften or liquefy in service, a gram sample of the grease is placed in a closed cylinder together with a weighted roller. The cylinderis then rotated for 4 hours at 160 r.p.m. A penetration test is run on the grease before and after the roll test and the amount of softening determined. An increase in penetration of more than 80 points indicates that the grease will probably not perform satisfactory in service.

The following examples are illustrative of the invention. In these examples, unless otherwise indicated, the mineral lubricating oil employed is a western naphthenic solvent-treated mineral lubricating oil having a viscosity at F. of 500 SUS and a V1. of 25.

Example I For purposes of comparison with the greases of this invention, a simple barium l2-hydroxy grease was prepared and its characteristics determined. A grease was prepared from the following materials.

I Octylated diphenylamines,

The l2-hydroxystearic acid and 400 grams of oil were charged to a small grease kettle provided with means for agitation and heating and the mixture heated to 202 F. To this heated mixture was added the barium hydrate and 50 grams of water and heating was continued while adding the remainder of the oil, the maximum temperature being about 330 F. The oxidation inhibitor was added during the addition of oil. The mixture was then cooled while being agitated. The product was very lumpy and non-homogeneous, however, it was smooth and homogenized by passing it three times through a three roll laboratory paint mill.

The product obtained in the above manner had a Shell micro penetration of 129 and an ASTM dropping point of 320 F. This product had a soap content of 23% by weight. When a portion of the grease was placed on a hot plate with a surface temperature between 325 F. and 350 F., considerable oil separation occurred and the mixture remained soft and granular after it had cooled and had been worked with a spatula. Obviously, the grease was not reversible, i.e., after being heated and cooled it lost its grease structure. In the Shell roll test, this grease softened about 100 points.

Example II A grease of this invention was prepared with the following ingredients:

A 50% concentrate in mineral lubricating oil 01 a boron ester prepared in the following manner. A mixture of 4.5% orthoboric acid and 45.5% of castowax (triglyceride or 12- hydroxystearic acid) and 50% lubricating oil was stirred and heated to 400 F. On cooling a hard mass was formed.

The l2-hydroxystearic acid and 400 grams of the mineral lubricating oil were charged to a grease kettle and heated with stirring to a temperature of 200 F. To this heated mixture the barium hydroxide and 50 ml. of water was added and heating continued for approximately 20 minutes. The remainder of the oil was added slowly A grease of this invention was prepared with the following ingredients:

Grams 12-hydroxystearic acid 300 Barium hydroxide pentahydrate 135 Mineral lubricating oil 1900 Boron ester compound a 85 Triethanolamine l I Same as Example II.

This grease was prepared following the method outlined in Example II. The triethanolamine was added during the final heating of the grease. v

The product had a soap content of 15.6%, a penetration of 126, an ASTM dropping point of 360 F., it softened points in the Shell roll test and it was reversible.

Example IV A grease of this invention was prepared with the following ingredients:

Grams 12-hydroxystearic acid 300 Barium hydroxide pentahydrate 135 Mineral lubricating oil 1500 Boron ester compound a 85 Triethanolamine 2 Same as Example II.

.This grease was prepared as described in Example II, the triethanolamine being added during the final heating of the grease.

This product had a soap content of 18.8%, a penetration of 126, an ASTM dropping point of 378 F. and was reversible.

Example V A grease of this invention was prepared with the following ingredients:

Grams 12-hydroxystean'c acid 300 Barium hydroxide pentahydrate 135 Mineral lubricating oil 2000 Phenyl alphanaphthylamine 5 Boron ester compound 35 I Solvent treated and dewaxed western paraflinic mineral lubricating oil of S.A.E. 30 grade.

mixture of 62.6 parts by weight of ethylene glycol dl- 12-hydroxy stearate and 6.2 parts by weight of orthoboric acid was stirred and heated to 375 F. and maintained at this temperature for about 20 minutes. This product was a solid mass when cooled.

This grease was prepared following the method described in Example II. The product contained about 15.3% of soap, had a penertation of 137, an AST M dropping point of 358 F. and softened 16 points in the Shell roll test. This grease was reversible.

Example VI A grease of this invention was prepared with the following ingredients:

Grams l2-hydroxystearic acid 300 Barium hydroxide pentahydrate 135 Mineral lubricating oil 2000 Phenyl alphanaphthylamine 5 Boron ester compound a 25 A mixture of 36 parts by weight of ethylene glycol mono- 12-hydroxystearate and 6 parts by weight of orthoboric acid was stirred and heated to 875 F, and maintained at this temperature for about 20 minutes. This product was a solid mass when cooled.

This grease was prepared following the method described in Example II. The product contained about 15% of soap, had a penetration of 141, an ASTM dropping point of 347 F. and softened 18 points in the Shell roll test. This grease was reversible.

Erample VII A grease of this invention was prepared with the following ingredients:

Grams 12-hydroxystearic acid 300 Barium hydroxide pentahydrate 135 Mineral lubricating oil 2000 Phenyl alphanaphthylamine 5 Boron ester compound 30 A mixture of 64 parts by weight of propyleneglycol di- 12-hydroxystearate and 6.3 parts by weight 01' orthoboric acid was stirred and heated to 375 F. and maintained at this temperature for about 20 minutes. This product was a solid mass when cooled.

This grease was prepared following the method described in Example II. The product contained about 15% of soap, had a penetration of 128, an ASTM dropping point of 350 F. and softened 21 points in the Shell roll test. This grease was reversible.

Example VIII A grease of this invention was prepared with the following ingredients:

Grams 12-hydzroxystearic acid 300 Barium hydroxide pentahydrate 135 Mineral lubricating oil 2000 Agerite Stalite 5 Boron ester compound 8 25 A mixture of 41 parts by weight of glycerol mono-9,10- dihydroxy stearate and 13 parts by weight of orthoboric acid was stirred and heated to 375 F., and maintained at this temperature for about 20 minutes. This product was a solid mass when cooled.

This grease was prepared following the method described in Example II. The product contained about 15% of soap, had a penetration of 146, an ASTM dropping point of 354 F. and softened 14 points in the Shell roll test. This grease was reversible.

Example IX Example VIII was repeated, however, during the heating following soap formation, 2 grams of triethanolamine was added to the grease. This product has a penetration of 130, an ASTM dropping point of 368 F. and softened 17 points in the Shell roll test. This grease was reversible as indicated by the hot plate test.

Example X A grease of this invention was prepared with the following ingredients:

Grams l2-hydroxystcaric acid 300 Barium hydroxide pentahydrate a 135 Mineral lubricating oil 2200 Agerite Stalite 5 Boron ester compound l The product obtained by heating a mixture of 150 grams of castor oil and 15 grams of boric acid to a temperature of 410 F. for a period of 30 minutes.

The grease was prepared following the method of Example II. The product had a penetration of about 143, an ASTM dropping point of 356 F. and softened 9 points in the Shell roll test. This grease was reversible.

Example XI A grease of this invention was prepared with the following ingredients:

Grams l2-hydroxystearic acid 300 Barium hydroxide pentahydrate Mineral lubricating oil 2200 Agerite Stalite 5 Boron ester compound a 70 I The product obtained by heating a mixture of 75 grams of triethyleneglycol di-12-hydroxystearate and 6.5 grams of boric acid to a temperature of 410 F, for a period of 30 minutes.

The grease was prepared following the method of Example II. The product had a penetration of about 148, an ASTM dropping point of 348 F. and softened 21 points in the Shell roll test. This grease was reversible.

Example XII A grease of this invention was prepared with the following ingredients:

Grams IZ-hydroxystearic acid 300 Barium hydroxide pentahydrate 135 Mineral lubricating oil 2200 Boron ester compound B 45 a The product obtained by heating a mixture of '80 grams of dlethylene glycol monorlcinoleate and 12 grams of boric acid to a temperature of 410 F. for a period of 30 minutes.

The grease was prepared following the method of Example II. The product had a penetration of about 150, an ASTM dropping point of 355 F., and softened 23 points in the Shell roll test. This grease was reversible.

Example XIII A grease of this invention was prepared with the following ingredients:

Grams l2-hydroxystearic acid 300 Barium hydroxide pentahydrate 135 Mineral lubricating oil 2200 Boron ester compound 5 The product obtained by heating a mixture of 80 grams of ethylene glycol dIQJO-(IIIIYdIOXYStGBIlItB and 14 grams of boric acid to a temperature of 410 F for a period of 30 minutes.

The grease was prepared following the method of Example II. The product had a penetration of about 162, an ASTM dropping point of 341 F. and softened 27 points in the Shell roll test. This grease was reversible.

Example X I V A grease of this invention was prepared with the following ingredients:

Grams l2-hydroxystearic acid 450 Barium hydroxide pentahydrate 202.5 Mineral lubricating oil 1500 Phenylalphanaphthylamine 5 Boron ester compound The boron ester compound used in the above formulation was prepared from a mixture of hydroxy fatty acids containing from about 8 to about 50 carbon atoms. This mixture of acids was obtained by oxidizing refined paraffin wax having a melting point of 145 F. in the liquid phase with air at a temperature of 255-265 F. and a pressure of 100 p.s.i. gage. Air blowing was continued until an acid number of 265 was obtained. This product was washed with water and with a petroleum naphtha leaving a water-insoluble naphtha-insoluble product. This fraction consisting of hydroxy acids and some neutral material was converted to its glycol ester by refluxing a mixture of the mixed acids and glycol with xylene and removing water. This product was reacted with boric acid in the ratio of 75 parts of glycol ester to 9 parts of boric acid at a temperature of.380 F. for 0.5 hours.

A grease was prepared following the procedure outlined in Example II. It had a penetration of 127, an ASTM dropping point of 347 F., softened in the Shell roll test 18 points and was reversible.

The above examples show the effect of adding the boron compounds of this invention alone or in combination with triethlanolamine to greases thickened with barium 12-hydroxy stearate. Whereas the product of Example I is nonreversible and softens badly in the Shell roll test, the products of Examples II-XIV, inclusive, which are made in accordance with the invention herein are all reversible, have good mechanical stability as indicated by the Shell roll test, have higher dropping points and lower penetrations for a given soap content than does the grease prepared without the addition of boron compounds or triethanolamine.

The foregoing examples and description of this invention are illustrative of the invention but are not to be considered as limiting the invention to the particular compositions shown, as other similar compositions obtained by varying the proportions of soap and boron compounds employed and by using other hydroxy fatty acid esters in preparing the boron ester compounds as well as such compositions containing small proportions of triethanolamine are included within this invention as set forth in the following claims.

I claim:

1. A lubricating grease consisting essentially of mineral lubricating oil thickened with about 3% to about 30% by weight of barium lZ-hydroxystearate and containing a small amount, sutficient to impart good mechanical stability and reversibility characteristics to said grease, of the reaction product, obtained by heating to a temperature between about 215 F. and about 425 F., of orthoboric acid and an ester selected from the class consisting of glycol and polyglycol, mono and diesters of hydroxy fatty acids having 8 to 50 carbon atoms and glycerol mono, di and tri-esters of hydroxy fatty acids having 8 to 50 carbon atoms.

2. A lubricating grease consisting essentially of mineral lubricating oil thickened with about 3% to about 30% by weight of barium l2-hydroxystearate and containing a small amount, sufficient to impart good mechanical stability and reversibility characteristics to said grease of the reaction product, obtained by heating to a temperature between about 215 F. and about 425 F., of orthoboric acid and an ester selected from the class consisting of glycol and polyglycol, mono and di-esters of hydroxy fatty acids having 8 to 50 carbon atoms and glycerol mono, di and tri-esters of hydroxy fatty acids having 8 to 50 carbon atoms, and a small amount of triethanolamine sufficient to further improve the mechanical stability of said grease.

3. A lubricating grease consisting essentially of mineral lubricating oil thickened with about 3% to about 30% by weight of barium lZ-hydroxystearate and containing between about 0.05% and about 5% by weight of the reaction product, obtained by heating to a temperature between about 215 F. and about 425 F., of orthoboric acid and an ester selected from the class consisting of glycol and polyglycol, mono and di-esters of hydroxy fatty acids having 8 to 50 carbon atoms and glycerol mono, di and tri-esters of hydroxy fatty acids having 8 to 50 carbon atoms.

4. A lubricating grease according to claim 1 in which said hydroxy fatty acids are 12-hydroxystearic acid.

5. A lubricating grease according to claim 1 in which said ester is glycerol tri-lZ-hydroxystearate.

6. A lubricating grease according to claim 3 containing between about 5% and about 20% by weight of soap.

7. A lubricating grease according to claim 3 containing also between about 0.01% and about 0.5% by weight of tri-ethanolamine.

8. A lubricating grease consisting essentially of mineral lubricating oil thickened with about 3% to about 30% by weight of barium lZ-hydroxystearate and containing between about 0.05% and about 5% by weight of the reaction product, obtained by heating to a temperature between about 215 F. and about 425 F., of 1 chemical equivalent, based on hydroxyl groups, of an ester selected from the class consisting of glycol and polyglycol, mono and di-esters of hydroxy fatty acids having 8 to 50 carbon atoms and glycerol mono, di and tri-esters of hydroxy 9 fatty acids having 8 to 50 carbon atoms, with 1.4 to 1.7 equivalents of orthoboric acid.

9. A lubricating grease according to claim 8 in which said reaction product is obtained by heating said ester and said orthoboric acid to a temperature between about 215 F. and about 425 F.

10. A lubricating grease consisting essentially of mineral lubricating oil thickened with about 5% to about 20% by weight, based on said grease, of barium l2-hydroxystearate and containing between about 0.1% and about 2.0% by weight of the reaction product, obtained by heating to a temperature between about 215 F. and about 425 F., of orthoborie acid and an ester selected from the class consisting of glycol and polyglycol, mono and di-esters of hydroxy fatty acids having 8 to 50 car- 15 2,815,325

References Cited in the file of this patent UNITED STATES PATENTS 2,049,072 Mikes-14a et al. July 28, 1936 2,361,391 Fraser et al. Oct. 31, 1944 2,503,749 Langer et al. Apr. 11, 1950 2,607,735 Sproule et al. 5. Aug. 19, 1952 Pohorilla et al. Dec. 3, 1957 

1. A LUBRICATING GREASE CONSISTING ESSENTIALLY OF MINERAL LUBRICATING OIL THICKENED WITH ABOUT 3% TO ABOUT 30% BY WEIGHT OF BARIUM 12-HYDROXYSTEARATE AND CONTAINING A SMALL AMOUNT, SUFFICIENT TO IMPART GOOD MECHANICAL STABILITY AND REVERSIBILITY CHARACTERISTICS TO SAID GREASE OF THE REACTION PRODUCT, OBTAINED BY HEATING TO A TEMPERATURE BETWEEN ABOUT 215*F. AND ABOUT 425*F., OF ORTHOBORIC ACID AND AN ESTER SELECTED FROM THE CLASS CONSISTING OF GLYCOL AND POLYGLYCOL, MONO AND DI-ESTERS OF HYDROXY FATTY ACIDS HAVING 8 TO 50 CARBON ATOMS AND GLYCEROL MONO, DI AND TRI-ESTERS OF HYDROXY FATTY ACIDS HAVING 8 TO 50 CARBON ATOMS. 